A two-alarm blaze that caused a vacant nightclub to collapse Sunday is under investigation by the Harris County fire marshal, who noted signs of forced entry.

"The building had been vacant for almost a year," said Lt. Dean Hensley, spokesman for the Harris County Fire Marshal's Office, about the roaring fire that demolished Club Bugatti in the 14700 block of Kuykendah in north Harris County.

The Ponderosa Fire Department began drenching the flames with water about 9 a.m. and took the next three hours to bring the fire under control.

Two firefighters became overheated and were treated at the scene, Hensley said.

The northbound lanes of Kuykendahl were cluttered with fire hoses and remained closed late Sunday afternoon.